what compression ratio

[ebo 4356]

Im buying a wiseco piston kit, because my rings are bad and the piston is worn. which compression ratio should run for stock bore.

i think highest you can run on pump gas is 11:1. my brother had a 10:1 and it was a big improvement vs stock. the Wiseco are much lighter than stock

[XXXRACER165]

yea go with 11:1, you will like it better downd the road when you do other mods to it.

[BlasterEaten250]

I regret not getting an 11:1 instead of my 10:1.

[ebo 4356]

So i can run 11:1 on 87, and how much more power will i gain.

[Pipeless416]

Originally posted by ebo 4356
So i can run 11:1 on 87, and how much more power will i gain.

you're supposed to run at least 91 with stock compression i think.. so with 11:1 you definitely need to stick to the highest octane pump gas.

[ebo 4356]

would 91 be alright

[GPracer2500]

Originally posted by ebo 4356
would 91 be alright

Maybe...probably...but 91 pump gas could turn out to not be enough. Most will tell you 11:1 pistons are ok on premium pump in the 400EX. But that wasn't my experience.

I built a 400EX with a 87mm 10.8:1 JE and an old style HC stg 2. It would knock on my local 91 pump gas. In the dunes the knocking was especially problematic.

For whatever reason the manufacturing tolerances on my cylinder, head, rod, piston, etc, the particular chemistry of my region's gasoline, my riding conditions, and other reasons all conspired to preclude pump gas on my build. That doesn't seem to be most peoples' experience but that's how it worked out for me. I emphasize seem because some times I wonder how many folks' engines will occasionally knock without them realizing it is happening [shrug]. Light knocking won't kill your engine in a hurry and can easily be overlooked as something innocuous. It should be avoided though.

$0.02

[slow96hater]

just make sure you rejet. unless it'll spark knock.

[97WarriorRider]

Is 11:1 to much for stock head bolts?

[ebo 4356]

So what wat compression ratio should i go with then, and will the stock engine be able to handle 11:1.

[f150mann]

stock bore, 11:1 wiseco will be fine. use a new head gasket regular size, and wiseco works out to be closer to 10.8:1, and 91 should be okay, 93 would be preferred but i only have 92 locally and it worked okay.

stock heads studs will be fine 95% of the time, and everything else will be okay, but i would check the cam chain and tensioner, make sure they are good, if not replace it with the crf one, well worth the 40 bucks

[97WarriorRider]

So the 11:1 in the end will only be 10.8:1?

[ebo 4356]

well i cant really afford 93 everytime so what if i got the wiseco 10:1, would still notice a gain in power.

Originally posted by ebo 4356
well i cant really afford 93 everytime so what if i got the wiseco 10:1, would still notice a gain in power.

wait your not running 93 octane gas? you should run 93 octane on a stock motor because the lower octane makes the gas predetonate

[ebo 4356]

well ive been running 87 in my 400 for 4 years now. And it still runs fine.

[f150mann]

if you cant afford the 2 dollars more for 93 octane, you are living in the projects man. wtf, that is such a minor cost run 93!!!

[red_rider_069]

how good does 12.5:1 run on 91?

[ebo 4356]

I got other things to pay for like my car im sorry im 17 workin and makin my own money. plus 93 around here cost 3.40 which is almost 20.00 dollars to fill up a 5 gallon gas can.

[ebo 4356]

will this work with my stock engine and could i use 91 octane with this piston.

http://cgi.ebay.com/ebaymotors/NEW-WISECO-HONDA-400EX-PISTON-KIT-10-1-STD-85-00mm_W0QQcmdZViewItemQQcategoryZ43977QQihZ010QQite mZ200175606010QQrdZ1QQsspagenameZWDVW

i feel your pain with high gas prices, tuesday for riding $20 got me just 6 gallons of gas. but 6 gallons is plenty of riding fr a 4 stroke. you should deffinately just get 92 or 93 otherwise you are just cheating your engine and predetonation isnt good. I ran 87 by accident and my stock 400ex ran like shat, it bogged down and had bad throttle response. i ran that tank out as quick as possible and filled it with 93 and no more bogging, it ran like it should

[ebo 4356]

yea i usally run 91, but what you think about that kit.

[ebo 4356]

i need an answer should go with the wiseco 11:1, or 10:1, and just one last time itll be ok on a stock engine, and how much more power should i notice on 93, and would 91 be ok.

[project400ex19]

Originally posted by ebo 4356
I got other things to pay for like my car im sorry im 17 workin and makin my own money. plus 93 around here cost 3.40 which is almost 20.00 dollars to fill up a 5 gallon gas can.

our 87 octane has finally dropped to 3.19...and i live in what is called the oil basin!

I refuse to run 87 in my quad i even run 90 in my car.

[JPC2075]

putting in a 440 kit what do i need to buy and change

[f150mann]

everyone has bills man, im 20, i have a mortgage, truck, car, quad, ski doo, etc payments.

my truck gets 12mpg on a good day, and gas is 4.03 a gallon here, so i know all too well about how expensive gas is.

but for the amount of riding you get out of a 20$ tank of fuel in a quad, who cares.

really, if you cant afford to pay 20$ for a tank of fuel, dont modify your quad at all. save your money for bread.